The prescaler is an important component for frequency configuration in the wireless communication systems, devices and applications. The prescaler provides multi-modulus divide ratio for the system to achieve wide operating frequency range to meet the flexible needs of the modern wireless communication systems.
However, the increasing higher transmission frequency limits the operating speed of the prescaler and increases the power consumption. U.S. Pat. No. 6,768,353 disclosed a prescaler device. The prescaler device provides the easily controlled multi-modulus divide ratio that can operate under 1 GHz and consumes only a little power. FIG. 1 shows a schematic view of a block diagram of the prescaler device.
As shown in FIG. 1, a prescaler device 100 includes a frequency divider 101, a plurality of series-coupled delay elements 111-11N, and a plurality of transmission gates 120-12N. Frequency divider 101 includes an input node 101a, and a divider output 101b. Frequency divider 101 is coupled with a clock signal and has a pre-determined divisor. Delay elements 111-11N are coupled with the divider output 101b and the clock signal. Each of the transmission gates 120-12N is coupled between the input node 101a and the delayed output of a corresponding delay element.
When a transmission gate is enabled and the delayed output of the m-th delay element is outputted to input node 101a, the output frequency of the divider of frequency divider 101 is equal to a clock frequency. The clock frequency is the one that is divided by the pre-determined divisor then plus m. In other words, the prescaler in FIG. 1 uses the delay to increase divisor, and executes 2n+m.
In designing the radio frequency (RF) phase-locked loop (PLL) for digital broadcasting, a prescaler divided by 30/31 must be included to achieve the frequency configuration of the system. However, this type of divisor cannot be efficiently implemented with the aforementioned simple prescaler. Therefore, the implementation of such a prescaler divided by 30/31 remains a challenge.